Optimum grassland nutrition can not only improve dry matter yields, it can also significantly extend intervals between re-seeding, says independent grassland specialist Dr. George Fisher.
Planning to get the maximum ROI (return on investment) from reseeding is a must with the three key elements being matching variety choice to sward management - for grazing and cutting - soil condition and general plant nutrition.
"Reseeding typically costs £450 – 500/ha but over a five year period, you can expect reseeded leys to produce a total of 624,000 MJ/ha of energy whereas for permanent pasture this will be more like 440,000MJ/ha.
"At 22p/litre, the revenues for total potential milk production from the reseeded grassland will be £25,422 compared to £17,925 for the permanent pasture, so the costs of the actual reseed is quickly repaid."
But key to taking full advantage of this potential extra return on investment is minimising the drop-off in grass energy produced as the new swards inevitably decline, he points out.
"Without adequate nutrition a new sward can lose the equivalent of 4,500 litres/ha of lost production every year."
"Modern grass varieties are able to use Nitrogen more efficiently but the fact that these plants remain stronger and more abundant means they compete better with other pernicious grass species and continue in the sward for longer."
"That means that as the years progress you’re more likely to have pasture that reflects the mix you put in at the start than if you try and cut corners with nutrition over those years. Plus you’re likely to get an extra 2-3 years out of your reseeding which will make it even more cost-effective."
Importance of Sulphur & Phosphorous
As well as managing Nitrogen properly, focusing on other key nutrients is increasingly high on the agenda for grassland producers, George Fisher says.
"Trials carried out by CF in 2016 show Sulphur delivered a 29% increase in grass growth for both first and second cuts on reseeds in the first full growing season."
"Like 2015, 2016 is a very Sulphur responsive year but we’ve seen significant responses to Phosphorus, too."
"The 2016 trials, which took place in Cheshire and Devon, followed CF trials from 2014/15 in which tangible and useful responses in grass yield to Sulphur, even on heavier soils, and to maintenance applications of Phosphorus on P index 2 and 3 soils, were seen."
In trials on medium loam soils in Cheshire, a 190kg/ha application of straight N (Nitram) delivered to a reseed gave of 9.66t DM/ha in total for first and second cut silage, whilst the addition of 84 kg/ha of Sulphate (SingleTop) lifted this to 12.45t DM/ha – a 29% increase.
On the same reseed, using Sulphur for grazing also produced an extra 1.1t DM/ha over the first four grazing rotations – a 14% yield response.
On a heavier clay loam at the Devon trials site, response to Sulphur was 10% for the same levels of application as the Cheshire site, whilst when Sulphur and Phosphorus were added together, yields increased from 4.2t DM/ha from the straight Nitrogen to 5.2t DM/ha – an impressive 24% lift.
According to CF Fertilisers’ Hefin Llywd the results are highly significant in light of growing the emphasis on getting the most out of home-grown feed.
"If you assume a 75% utilisation rate from field to feeding, the extra 2.8t/ha DM in Cheshire for first and second cut silage at 11 MJ ME contains enough energy to produce 4,200 litres of milk or 490kg of liveweight gain. Well worth having."
"Similarly, an extra 1.1t/ha DM for early grazing at 12 MJ ME and an 85% utilisation rate, produces enough energy to produce an 2,000 litres of milk or 240kg liveweight."
The responses to Phosphorus are also very interesting with an application of 40kg P2O5 (water soluble phosphate) giving 9% more grass DM yield on first and second cut silage and 5% on the first four grazings, he points out.
"These responses are occurring when soil P indexes are already at 2 and 3, suggesting that maintenance applications of P in this form are used efficiently and provide a beneficial yield response."
"All in all, the cost/benefit in milk production shows a £20 return for every £1 spent on Sulphur and up to £12 for every £1 on Phosphorus."